Currently, many tapes and other pressure-sensitive adhesive-coated articles have a release liner applied to the adhesive during or following manufacture. The release liner is typically left in place while the article is laminated, converted, packaged, and shipped to ultimate users, and in many instances is left in place until the article is bonded to an adherend with the pressure-sensitive adhesive. Release liners are often used for one or more of a number of purposes, including, for example, preventing contamination of the adhesive layer, facilitating handling of the adhesive-coated article (e.g., by providing support thereto as well as covering the adhesive), identifying the articles to which they are applied, providing roll stability of articles such as tapes when wound into roll form, etc.
The state-of-the-art in release liner technology for ultra high performance acrylic pressure-sensitive tapes is polyethylene or polypropylene films. These films have been successfully used for many years because they do not require a release coating (e.g. silicones) and can be formulated to possess sufficient stiffness (secant modulus) to support the tape construction through processing, converting, and lamination. Secant modulus has been used for years to predict the processability of a particular liner/tape construction. It relates to the initial stiffness of a film and indicates the ability of a film to support a pressure-sensitive tape through all aspects of processing.
As applications have evolved, conventional polyolefin-based release liners have not been capable of supporting the tape construction sufficiently to avoid stretching the tape during the manufacturing or lamination processes. Conventional liners exhibit a yielding behavior that allows the tape to stretch or elongate by as much as 12+% during the lamination phase of manufacturing. This amount of stretch is a major contributor to liner pop-off in low modulus, pressure-sensitive tape constructions. Strain induced pop-off results from a differential level of stress between the pressure-sensitive tape construction and the polyolefin release liner. In addition to liner modulus, time, temperature, handling, and packaging all contribute to the pop-off problem.
What is needed in the industry is a release liner which greatly minimizes and/or eliminates the pop-off problem and which controls the stretch of the tape during manufacturing operations subsequent to the lamination of the tape to the release liner.